Measurement of Angle Kappa With Synoptophore and Orbscan II in a Normal Population

Intraocular lens power calculation: angle κ and ocular biomechanics

PURPOSE

To study the effect of ocular biomechanics on the prediction error of intraocular lens (IOL) power calculation.

SETTING

Centro Hospitalar Universitário do Porto, Porto, Portugal.

DESIGN

Prospective longitudinal study.

METHODS

This study included 67 subjects. Before cataract surgery subjects underwent biometry with IOLMaster 700 and biomechanical analysis with Corvis Scheimpflug technology. The targeted spherical equivalent was calculated with SRK-T and Barrett Universal II. Associations between prediction error (PE), absolute prediction error (AE), and biometric and biomechanical parameters were performed with stepwise multivariate linear correlation analysis.

RESULTS

Using the SRKT formula, there was association between PE and Corvis Biomechanical Index (CBI, B = -0.531, P = .011) and between AE and the horizontal offset between the center of the pupil and the visual axis (angle κ, B = -0.274, P = .007). Considering the Barret Universal II formula, PE was independently associated with anterior chamber depth ( B = -0.279, P = .021) and CBI ( B = -0.520, P = .013) and AE was associated with angle κ ( B = -0.370, P = .007).

CONCLUSIONS

A large angle κ may reduce the predictability of IOL power calculation. Ocular biomechanics likely influence the refractive outcomes after IOL implantation. This study showed that eyes with softer corneal biomechanics had more myopic PE. This may relate to anteriorization of the effective lens position. Dynamic measurements may be the way to progress into future formulas.

Measurement of the distance between corneal apex and pupil center in patients following small-incision lenticule extraction or implantable collamer lens implantation and its correlation with the surgical-induced astigmatism

BACKGROUND

To investigate the change in the distance between corneal apex and pupil center after small-incision lenticule extraction (SMILE) or implantable collamer lens (ICL) implantation and its correlation with surgical-induced astigmatism (SIA).

METHODS

This study included patients who had undergone SMILE (n = 112) or ICL implantation (n = 110) to correct myopia and myopic astigmatism. The angle kappa was measured using a Scheimpflug imaging device (Pentacam) and represented as Cartesian values between the pupil center and the corneal vertex (X, Y) and chord u ([Formula: see text]orientation), and was compared pre- and post-operative.

RESULTS

Following SMILE, the magnitude of chord u[Formula: see text]) significantly increased in both eyes (Wilcoxon signed-rank test, OD: P<0.001; OS: P=0.007), while no significant change was observed in the orientation. A significant correlation was found between the J0 component of SIA and the change in the magnitude of chord u for both eyes (OD: R2=0.128, P<0.001; OS: R2=0.033, P=0.004). After ICL implantation, the orientation of the chord u was significantly different in the right eye (Wilcoxon signed-rank test, P = 0.008), and the Y-intercept significantly decreased in both eyes (Wilcoxon signed-rank test, P<0.001). A significant correlation was found between J0 of SIA and the change in the magnitude of chord u for the right eyes (R2=0.066, P=0.002). A significant correlation was found between J45 of SIA and the change in the magnitude of chord u for the left eyes (R2=0.037, P=0.044).

CONCLUSIONS

The magnitude of the chord u increased following the SMILE procedure, whereas the Y-intercept significantly decreased after ICL implantation. SIA was related to the change in the magnitude of chord u.

Differences in the perception of direct gaze between the externally and internally rotated eye

The perception of direct gaze provides multiple benefits for the observer. Previous studies have investigated how the information from both eyes is used to estimate gaze direction, showing that the perception of gaze direction differs when only the externally rotated eye versus only the internally rotated eye is visible. We examined the width and center of the area of direct gaze by presenting the observers with either the externally or internally rotated eye, or both eyes with the task to judge whether a computer avatar is looking at them. Two experiments yield evidence for a wider area of direct gaze for the externally rotated eye (around 6°) than for the internally rotated eye (around 4°). The area of direct gaze for both eyes was found to be the same as for the internally rotated eye, but smaller than for the externally rotated eye. When both eyes were present, our results indicate that the perception of direct gaze is more likely to follow the internally rotated eye. The discussion substantiates a new generalization that observers base their judgments on the more rotated eye, which can differ due to angle kappa and vergence, in our study it is the internally rotated eye.

A low-cost robotic oculomotor simulator for assessing eye tracking accuracy in health and disease

Eye tracking accuracy is affected in individuals with vision and oculomotor deficits, impeding our ability to answer important scientific and clinical questions about these disorders. It is difficult to disambiguate decreases in eye movement accuracy and changes in accuracy of the eye tracking itself. We propose the EyeRobot-a low-cost, robotic oculomotor simulator capable of emulating healthy and compromised eye movements to provide ground truth assessment of eye tracker performance, and how different aspects of oculomotor deficits might affect tracking accuracy and performance. The device can operate with eccentric optical axes or large deviations between the eyes, as well as simulate oculomotor pathologies, such as large fixational instabilities. We find that our design can provide accurate eye movements for both central and eccentric viewing conditions, which can be tracked by using a head-mounted eye tracker, Pupil Core. As proof of concept, we examine the effects of eccentric fixation on calibration accuracy and find that Pupil Core's existing eye tracking algorithm is robust to large fixation offsets. In addition, we demonstrate that the EyeRobot can simulate realistic eye movements like saccades and smooth pursuit that can be tracked using video-based eye tracking. These tests suggest that the EyeRobot, an easy to build and flexible tool, can aid with eye tracking validation and future algorithm development in healthy and compromised vision.

Repeatability and Agreement of Chord Mu between Scheimpflug Tomography and Swept-Source Optical Coherence Tomography

PURPOSE

To evaluate repeatability and agreement of chord mu between Scheimpflug tomography (Pentacam HR) and sweptsource optical coherence tomography-based optical biometer (IOLMaster 700).

METHODS

In this retrospective study, 63 eyes from 33 patients were included. Chord mu, X and Y Cartesian distances between the corneal vertex and the pupil center (Px and Py), and the pupil diameter were compared using two instruments. Repeatability was evaluated using intraclass correlation coefficient (ICC), coefficient of variation (CoV), and within-subject standard deviation (Sw). Interdevice agreement was evaluated using paired t-tests and Bland-Altman plots.

RESULTS

Although Sw values for all parameters were similar between the two devices, CoV values of chord mu and pupil diameter were lower, and ICC values of those parameters were higher, in the IOLMaster 700 than in the Pentacam HR. Chord mu and pupil diameter values were higher in IOLMaster 700 than Pentacam HR (p < 0.01). The width of the 95% limit of agreement was wide for all parameters.

CONCLUSIONS

IOLMaster 700 showed better repeatability than Pentacam HR in chord mu, Px, Py, and pupil diameter values. Because there were statistically significant differences and a low level of agreement in chord mu and pupil diameter values between the two devices, they cannot be used interchangeably.

Angle Kappa Influence on Multifocal IOL Outcomes

PURPOSE

To characterize angle kappa and study the relationship between preoperative angle kappa and postoperative refractive accuracy, visual outcomes, and patient satisfaction in a large population of eyes with multifocal intraocular lens (MIOL) implantation.

METHODS

A comprehensive electronic medical record chart review of 26,470 consecutive eyes that underwent immediate sequential bilateral cataract or refractive lens exchange with MIOLs was conducted. The primary outcome measures were postoperative monocular uncorrected distance visual acuity (UDVA), manifest refraction sphere and cylinder, spherical equivalent (SEQ), defocus equivalent (DEQ), subjective quality of vision at near, intermediate, and distance, and the likelihood of recommending the procedure. Relationships between preoperative angle kappa and postoperative outcomes were assessed with Pearson correlations.

RESULTS

Angle kappa followed a right-skewed normal distribution (R2 = 0.99) with a mean ± standard deviation of 0.64 ± 0.27 mm. No clinically meaningful relationship was found between preoperative angle kappa and postoperative sphere, cylinder, SEQ, and DEQ, all with R2 ⩽ 0.0005. Similarly, there was no clinically meaningful relationship between preoperative angle kappa and postoperative UDVA (R2 = 0.001), postoperative satisfaction for near, intermediate, and distance vision (all R2 ⩽ 0.0023), or for recommending the MIOL surgery to friends and relatives (R2 = 0.0000).

CONCLUSIONS

Preoperative angle kappa does not have a predictive clinical impact on postoperative MIOL visual outcomes, refractive accuracy, or subjective patient satisfaction. Angle kappa as a single variable cannot be used to determine MIOL candidacy. [J Refract Surg. 2023;39(12):840-849.].

The effect of different angle kappa on higher-order aberrations after small incision lenticule extraction

This study aimed to compare higher-order aberrations (HOAs) after small incision lenticule extraction (SMILE) in patients with different angle kappa. This is a retrospective report in which 341 right eyes of 341 patients who were subjected to SMILE, which used coaxially sighted corneal light reflex (CSCLR) as the treatment zone centered, treated by the same experienced surgeon (LHB) for correction of myopia and myopic astigmatism, preoperative and postoperative spherical equivalent (SE), angle kappa, total higher-order aberrations (total HOA), spherical aberration (SA), vertical coma (VC), horizontal coma (HC), oblique trefoil (OT), and horizontal trefoil (HT), were compared. SMILE showed outstanding performance in terms of safety, efficacy, and predictability. In addition, a comparison of preoperative and postoperative HOAs exhibited the difference of total HOA (P < 0.01), SA (P < 0.01), VC (P < 0.01), and HC (P < 0.01), which was statistically significant; however, for OT and HT with the longer follow-up time, the statistical difference gradually decreased. For stratification of angle kappa into groups based on decantation, angle kappa was divided into three major groups: r < 0.1 mm, 0.1 ≤ r < 0.2 mm, and r ≥ 0.2 mm; the changes of SA (F = 4.127, P = 0.021) and OT (F = 3.687, P = 0.031) exhibited significant difference after 1 year of SMILE. We performed a correlation analysis of all preoperative and postoperative parameters, and the results indicated that the preoperative total HOA was negatively correlated with preoperative cylindrical diopter (DC), and postoperative total HOA, SA, and coma were affected by spherical diopter (DS) and SE. Moreover, we also found a significant difference of SA and VC in the early postoperative with preoperative. SA was positively correlated with Y values and r of 1 year after SMILE. All of the analyzed parameters in the three groups, except for the trefoil, gradually increased over time; however, the trefoil could gradually stabilize over time. We also divided angle kappa into four groups by quadrants; the result showed that the effects of higher-order aberrations were markedly different from the various quadrants. Patients with large angle kappa were able to increase VC and SA postoperatively, and higher HOAs were more significant in patients with high myopia. The differences in quadrants exhibited a diversity of HOAs; this could be attributed to the corneal surface reestablishment and the alteration of angle kappa, but the trend was not apparent. Although all patients displayed increased HOAs after SMILE, the potential application of CSCLR as the treatment zone centered still showed excellent safety, efficacy, and predictability.

Are the directions of both eyes integrated before or after the perception of direct gaze? Evidence from simulated mild strabismus

The cone of gaze is a looker's range of gaze directions that is accepted as direct by an observer. The present research asks how the condition of mild strabismus, that is, when the two eyes point in slightly different directions, influences the cone of gaze. Normally, both eyes are rotated in a coordinated manner such that both eyes are directed to the same fixation point. With strabismus, there are two fixation points, and, therefore, two directions into which the two eyes point. This raises the question of the direction and the shape (i.e., width) of the gaze cone. Two experiments are conducted with simulated mild strabismus. Three conditions are tested, the two strabismic conditions of esotropia, and exotropia and one orthotropic (nonstrabismic) condition. Results show that the direction of the gaze cone is roughly the average of the directions of the two eyes. Furthermore, the width of the gaze cone is not affected by simulated strabismus and is thus the same for the strabismic and the orthotropic conditions. The results imply a model where at first the direction of gaze based on both eyes is perceived, and where the gaze cone is implied on the basis of the combined gaze direction.

Assessment of Pupil Size and Angle Kappa in Refractive Surgery: A Population-Based Epidemiological Study in Predominantly American Caucasians

Purpose This retrospective study aims to establish normative values for pupil size, angle kappa, higher-order aberration, and astigmatism type in a largely Caucasian population in Utah, United States, utilizing the NIDEK OPD-Scan III system (Gamagori, Japan). Methods This study included 716 patients (1432 eyes) grouped based on spherical equivalence and age. Measurements were conducted under mesopic and photopic conditions. Statistical analysis involved Pearson's correlation and linear regression using the generalized estimating equation. NIDEK OPD-Scan III measured mesopic and photopic pupil size and angle kappa. The subjects were then grouped based on their spherical equivalence in diopters (D) and age in decades. The spherical equivalence groups were defined: >-6 D, -5.99 to -3 D, -2.99 to -0.25 D, -0.24 to 0.24 D, and >0.25 D (range 0.25-5.75 D). The higher-order aberration groups were based on the reason for the visit: laser-assisted in situ keratomileusis, photorefractive keratectomy, and small incision lenticule extraction as one group; cataract evaluation; and keratoconus. Astigmatism measurements were grouped into with-the-rule (WRT), against-the-rule (ATR), and oblique astigmatism, with further subgrouping into a young cohort (20-40 years) and an old cohort (>65 years).  Results Among 716 participants, 49.2% were men; the mean age was 42.1±15.5 (range 7-88 years). The average spherical equivalence for myopia eyes was -3.28±2.34 D, and 1.51±1.46 D for hyperopia eyes. The mean mesopic pupil size was 5.68 ± 1.09 mm; the photopic pupil size was 4.65±1.09 mm. Pearson's correlation coefficient for mesopic pupil size versus age was -0.551, and -0.42 for photopic pupil (p < 0.001); sphere vs mesopic pupil size was -0.200, and -0.173 for photopic pupil (p < 0.001). The regression analysis for mesopic pupil size versus age revealed a 0.39 mm decrease in average pupil size per decade increase in age, and 0.25 mm decrease per decade for photopic pupil. The regression analysis for mesopic pupil size versus sphere revealed a 0.22 mm decrease in average pupil size per 3D increase in sphere, and a 0.16 mm decrease 3 D increase in sphere for the photopic pupil. The mean mesopic angle kappa was 0.33 ± 0.15 mm; photopic angle kappa was 0.31±0.15 mm. Pearson's correlation coefficient for mesopic angle kappa vs spherical equivalence was 0.32, and 0.296 for photopic angle kappa (p <0.001 for both). Regression analysis for mesopic angle kappa vs spherical equivalence demonstrated a 0.051 mm increase in angle kappa per 3 D increase in spherical equivalence, and a 0.048 mm increase for photopic angle kappa (p < 0.001 for both). Among the higher-order aberration groups, the keratoconus group exhibited the highest levels. In terms of astigmatism type, WRT astigmatism was the most common in the young cohort, while ATR astigmatism was most prevalent in the older cohort. Conclusions The results of this study reveal significant associations between pupil size and increasing age, as well as between pupil size and increasingly positive refractive errors. These findings hold particular clinical relevance to older patients and individuals with hyperopia, as they undergo photoablative corneal refractive surgery or multifocal intraocular lens implantation. Understanding the established normative values for pupil size, angle kappa, higher-order aberration, and astigmatism type can aid clinicians in making more informed decisions and improving patient outcomes.

Visual satisfaction with progressive addition lenses prescribed with novel foveal fixation axis measurements

Progressive addition lens (PAL) prescription is usually conducted using the pupillary centre as a reference, which in general does not coincide with the visual axis (kappa distance), and this difference could induce undesired prismatic effects in far and near vision distances and adaptation problems. This study aimed to assess the impact on subjects' visual satisfaction with PALs prescribed based on foveal fixation axis (FFA) measurements. Two different PALs (LifeStyle 3i, Hoya Lens Iberia) were randomly prescribed [one with a customized inset (the difference between the FFA measurements (Ergofocus®, Lentitech, Spain) at far and near distances and the second with a standard inset (2.5 mm)] to be used by 71 healthy presbyopic volunteers in a prospective double-masked crossover clinical study involving one month of use of each PAL. Patients were self-classified into four groups according to their previous experience with PALs: neophyte, PAL users, PAL drop-out, and uncomfortable PAL users. Visual function and overall satisfaction with each PAL were collected and compared. Ninety-seven percent (95% CI 93-100%) of participants successfully adapted to PALs prescribed with FFA without significant differences (P = 0.26) among the study groups (100% neophyte and uncomfortable PAL users (95% CI 100% in both groups), 89% (95% CI 67-100%) PAL users and 94% (95% CI 82-100%) PAL drop-out group). There were no statistically significant differences in visual function (P > 0.05) between customized and standard inset PALs. Customized and standard inset lenses showed similar satisfaction (P > 0.42) that increased significantly (P < 0.01 without any carry-over effect) after 30 days of wear. PALs prescribed with FFA measurements showed high visual satisfaction, suggesting that these measurements are suitable for prescribing PAL adaptation processes. Additional research is necessary to assess differences in PAL users' performance with different prescription methods and lens designs.

The Impact of Angle Lambda on Patient Satisfaction after Optiflex Trio Trifocal Intraocular Lens Implantation

Purpose

To evaluate the vision-related quality of life (QOL), visual acuities, and refractive outcomes of patients with different angle lambda (λ) after a trifocal intraocular lens (IOL) implantation at Veni Vidi Eye Hospital, İstanbul, Turkey.

Methods

This retrospective, nonrandomized, and noncomparative case series included patients who had phacoemulsification bilaterally with the implantation of a trifocal IOL (Optiflex Trio) and responded to a vision-related QOL questionnaire measuring patient satisfaction. The patients were divided into two groups according to the angle λ with a cutoff value of 0.5 mm. Evaluations were conducted to examine the monocular visual acuities, spherical equivalents, corneal astigmatism measured 3 months after surgery, and outcomes of the QOL questionnaire in the two groups.

Results

The study examined 130 eyes from 65 patients aged from 41 to 78 years old. There were no statistically significant differences between the two groups at 3 months after surgery in terms of uncorrected distance visual acuity (UDVA), monocular uncorrected intermediate visual acuity (UIVA), monocular uncorrected near visual acuity (UNVA), spherical equivalent, and corneal astigmatism (P > 0.05). Patients with a greater angle λ had significantly more difficulty going out to see movies, plays, or sporting events (P=0.02), driving at night (P=0.002), and driving in difficult conditions (P < 0.001) than patients with a lower angle λ.

Conclusions

The Optiflex Trio showed good results in terms of visual acuity at all distances, positive refractive outcomes, and high patient satisfaction in daily life according to the QOL questionnaire. An angle λ greater than 0.5 mm may potentially cause dysphotopsia symptoms, especially during nighttime activities.

Effect of preoperative pupil offset on corneal higher-order aberrations after femtosecond laser-assisted in situ keratomileusis

BACKGROUND

This study aimed to investigate the relationship between multiple higher-order aberrations (HOAs) subgroups and pupil offset, as well as to analyze the factors affecting postoperative corneal HOAs in patients with different degrees of refractive errors.

METHODS

We enrolled 160 patients (316 eyes) aged ≥ 18 years who had undergone femtosecond laser-assisted in situ keratomileusis (FS-LASIK) treatment. Based on the relationship between the preoperative pupil offset and the postoperative ΔHOAs, all patients were divided into two groups: group I (pupil offset ≤ 0.20 mm) and group II (pupil offset > 0.20 mm). All of the eyes had low to high myopia with or without astigmatism (manifest refraction spherical equivalent (MRSE) < -10.00 D). Uncorrected distance visual acuity, corrected distance visual acuity, MRSE, pupil offset, central corneal thickness, corneal HOAs, vertical coma (Z₃^-1), horizontal coma (Z₃¹), spherical aberration (Z₄⁰), trefoil 0° (Z₃³), and trefoil 30° (Z₃^-3) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and at 1 and 3 months postoperatively.

RESULTS

Our result revealed significant differences in postoperative corneal total root mean square (RMS) HOAs, RMS vertical coma, RMS horizontal coma, RMS spherical aberration, and RMS trefoil 30° between group I and group II. ΔMRSE was found to be an effective factor for ΔRMS HOAs (R² = 0.383), ΔRMS horizontal coma (R² = 0.205), and ΔRMS spherical aberration (R² = 0.397). In group II, multiple linear regression analysis revealed a significant correlation between preoperative pupillary offset and Δtotal RMS HOAs (R² = 0.461), ΔRMS horizontal coma (R² = 0.040), and ΔRMS trefoil 30°(R² = 0.089). The ΔRMS vertical coma effect factor is the Y-component, and the factor influencing ΔRMS spherical aberration was ΔMRSE (R² = 0.256).

CONCLUSION

A small pupil offset was associated with a lower induction of postoperative corneal HOAs. Efforts to optimize centration are critical for improving surgical outcomes in patients with FS-LASIK.

Evaluating Changes in Apparent Chord Mu after Pharmacological Pupil Dilatation

INTRODUCTION

Preoperative measurements of apparent chord mu length above 0.6 mm have been associated with higher risks for photic phenomena after cataract surgery with multifocal intraocular lenses (MFIOLs).

METHODS

This retrospective study evaluated patients scheduled for elective cataract surgery at a single tertiary medical center between 2021 and 2022. Pupil diameter and apparent chord mu length were analyzed for eyes with biometry measurements from IOLMaster 700 (Carl Zeiss Meditec, AG) under photopic light conditions, before and after pharmacological pupil dilatation. Exclusion criteria were visual acuity worse than 20/100, prior intraocular surgery, refractive surgery, iris-related procedures, or pupil abnormalities affecting dilatation. Apparent chord mu lengths before and after pupil dilatation were compared. In addition, multivariate linear regression analysis, using a stepwise method, was conducted to assess possible predictors of apparent chord values.

RESULTS

Included were 87 eyes of 87 patients. Mean chord mu length increased after pupillary dilatation from 0.32 ± 0.17 mm to 0.41 ± 0.17 mm for right eyes (p < 0.001) and from 0.29 ± 0.16 mm to 0.40 ± 0.22 mm for left eyes (p < 0.001). Seven eyes (8.0%) had an apparent chord mu of 0.6 mm and above pre-dilatation. Fourteen eyes (16.1%) with an apparent chord mu under 0.6 mm pre-dilatation had apparent chord mu of 0.6 mm or above post-dilatation.

CONCLUSION

Apparent chord mu length significantly increases after pharmacological pupillary dilatation. Pupil size and dilatation status should always be considered during patient selection for a planned MFIOL using apparent chord mu length as a reference marker.

Methods of Corneal Vertex Centration and Evaluation of Effective Optical Zone in Small Incision Lenticule Extraction

Inappropriate small incision lenticule extraction (SMILE) centration methods can affect the decentration of the effective optical zone (EOZ) after operation, which can subsequently lead to the decline of postoperative visual quality. We aimed to provide an overview of corneal vertex (CV) centration methods and an evaluation of the size and decentration of the EOZ in SMILE. We described the CV centration methods for patients with myopia, myopic astigmatism, hyperopia, and large kappa angle. The measurement methods of the EOZ were evaluated from the aspects of corneal morphology and corneal refractive power. Additionally, we summarized the advantages and disadvantages of measuring decentration based on topographic mapping and intraoperative video-captured images. Finally, we discussed the relationship between the EOZ and visual quality. Based on our review, clinicians should consider the following when choosing CV centration methods and evaluating EOZ postoperatively. First, the tear film mark center or topographic map comparison method is preferred for the correction of myopia, low myopic astigmatism, hyperopia, and large kappa angle (>0.2 mm). Triple marking centration is recommended for high myopic astigmatism (-3.5 diopters). Second, the total corneal power better reflects the change in refractive power than the topographic method. The measurement of the area rather than the diameter of the total corneal refractive power is more suitable for the evaluation of noncircular EOZs after high myopia astigmatism (<-2.0 diopters). Third, for the evaluation of decentration, the tangential curvature difference map method is preferred as it is not influenced by offset pupils. Finally, a large EOZ after SMILE may improve patient tolerance to decentration.

Intrasession repeatability and agreement of a new method to measure the foveal fixation axis

Purpose

Ophthalmic lens adaptation, particularly with progressive addition lenses, requires accurate measurements of the patient nasopupillary distance (NPD) and interpupillary distance (IPD), which are usually collected using the pupil centre as a reference. However, differences between the pupil centre and visual or foveal axis could induce some subsidiary effects of correcting lenses. This study aimed to assess the intrasession repeatability of a new prototype (Ergofocus®; Lentitech, Barakaldo, Spain) that can measure the foveal fixation axis (FFA) distance and assess the agreement with the NPD measurements collected using a traditional method (frame ruler).

Methods

The FFA at far and near distances was measured three consecutive times in 39 healthy volunteers to determine the intrasession repeatability according to the British Standards Institute and International Organization for Standardization. Additionally, the FFA and NPD (standard frame ruler) were measured in 71 healthy volunteers and compared using Bland-Altman analysis. Two blinded experienced practitioners conducted each FFA and NPD measurement.

Results

The FFA measurements showed acceptable repeatability at far distances (right eye (RE): Sw = 1.16 ± 0.76 mm and coefficient of variation (CV) = 3.92 ± 2.51%; left eye (LE) Sw = 1.11 ± 0.79 mm and CV = 3.76 ± 2.51%) and at near distances (RE: Sw = 0.97 ± 0.85 mm and CV = 3.52 ± 3.02%; LE: Sw = 1.17 ± 0.96 mm and CV = 4.54 ± 3.72%). Additionally, agreement with the NPD showed large differences at far distances (RE: -2.15 ± 2.34, LoA = -6.73 to 2.43 mm (P < 0.001); LE: -0.61 ± 2.62, LoA = -5.75 to 4.53 mm (P = 0.052)) and near distances (RE: -3.08 ± 2.80, LoA -8.57 to 2.42 mm (P < 0.001); LE: -2.97 ± 3.97, LoA: -10.75 to 4.80 mm (P < 0.001)).

Conclusions

FFA measurements showed clinically acceptable repeatability at both far and near distances. Agreement with the NPD measured using a standard frame ruler showed significant differences, suggesting that both measurements are not interchangeable in clinical practice to prescribe and center ophthalmic lenses. Further research is necessary to assess the impact of FFA measurement in ophthalmic lens prescriptions.

Supplementary Implantation of 1stQ AddOn® Sulcus-Fixated Intraocular Lens to Treat Negative Dysphotopsia: A Retrospective Case Series

Negative dysphotopsia (ND) refers to the subjective perception of an arc-shaped darkness or shadow in the temporal field of vision. This condition occurs after uneventful cataract surgery with an in-the-bag intraocular lens (IOL). To address this issue, supplementary implantation of conventional three-piece IOLs in the sulcus or dedicated supplementary Rayner Sulcoflex® IOL have been used successfully. The aim of this retrospective case series was to assess the effectiveness of resolving ND using a supplementary 1stQ AddOn® (Medicontur) IOL. The 1stQ AddOn® has a different design and optic size compared to the Rayner Sulcoflex®. Patients experiencing severe and persistent ND underwent supplementary implantation of the 1stQ AddOn® IOL. The primary outcome measure was the resolution of dysphotopsia. Nine eyes received the 1stQ AddOn® IOL, with complete symptom resolution observed in 6 eyes, partial improvement in 1 eye, and no change in 2 eyes. This indicates that supplementary implantation of the 1stQ AddOn® IOL can effectively and safely treat ND, performing equally well as the Rayner Sulcoflex®. The positive impact of sulcus-fixated supplementary IOLs seems to be related to the interaction between the central optic and the pupil margin.

Reliability and agreement of apparent chord mu measurements between static and dynamic evaluations

PURPOSE

To assess the repeatability and agreement of Cartesian coordinates and the length of apparent chord mu and pupil diameter measurements during static (Galilei G4) and dynamic (Topolyzer Vario) evaluations.

SETTING

IOBA-Eye Institute, Valladolid, Spain.

DESIGN

Case series.

METHODS

3 consecutive measurements per scenario (Galilei G4 and Topolyzer Vario under low mesopic and photopic conditions) were performed by the same clinician. The intrasession repeatability was assessed using the within-subject SD (Sw), the precision, the coefficient of variation, and the intraclass correlation coefficient (ICC). The agreement was analyzed using repeated-measures analysis of variance and the Bland-Altman method.

RESULTS

Thirty-seven healthy participants were recruited. The Sw values for chord mu parameters and pupil diameter ranged from 0.01 to 0.03 and 0.08 to 0.21, respectively. The ICC was ≥0.89 for all parameters. Galilei G4 and Topolyzer Vario under low mesopic and photopic conditions provided significantly different measures of apparent chord mu length (0.23 ± 0.11 mm, 0.30 ± 0.10 mm, and 0.25 ± 0.11 mm, respectively, P ≤ .02), X-coordinate (-0.18 ± 0.12 mm, -0.27 ± 0.11 mm, and -0.21 ± 0.12 mm, respectively, P < .001), and pupil diameter (3.38 ± 0.50 mm, 6.29 ± 0.60 mm, and 3.04 ± 0.41 mm, respectively, P < .001). Y-coordinate values obtained by Galilei G4 and Topolyzer Vario under low mesopic conditions were significantly different (0.06 ± 0.13 mm vs 0.03 ± 0.11 mm, respectively, P = .02), in contrast to Galilei G4 and Topolyzer Vario under photopic conditions (0.05 ± 0.13 mm, P = .82) and both illumination conditions of Topolyzer Vario (P ≥ .23).

CONCLUSIONS

Galilei G4 and Topolyzer Vario provide consistent measurements of apparent chord mu Cartesian coordinates and length, as well as pupil diameter; however, the measurements are not interchangeable. Ophthalmic surgeons should consider these findings when planning customized intraocular lens implantation and refractive surgery procedures.

Distribution of angle lambda and pupil offset as measured by combined Placido Scheimpflug Topography

BACKGROUND

Angle lambda is the angle between the pupillary axis and the line of sight. It is important for accurate centration during anterior segment surgery. The purpose of this study is to identify the distribution of angle lambda and pupil center offset as measured by a combined placido disc Scheimpflug topography system.

METHODS

A prospective non-randomized study was performed on 2178 eyes in Eye World Hospital, Giza, Egypt. Sirius device (CSO, Costruzione Strumenti Oftalmici, Florence, Italy, version 3.2.1.60) was used to measure average keratometry (K), anterior chamber depth (ACD), central corneal thickness (CCT), horizontal visible iris diameter (HVID), pupil radius (PR), pupil center intercept x-component (PCI-x), and pupil center intercept y-component (PCI-y). Axial length (AL) was measured by immersion A-scan Eyecube Ultrasonography device (Ellex, Adelaide, South Australia, Australia). Angle lambda was calculated by a trigonometrical equation. Pearson correlation was used to analyze the correlation between angle lambda and age and refraction.

RESULTS

Average angle lambda in all eyes was 3.32° ± 1.99. Mean angle lambda was significantly smallest in myopia and largest in hyperopia. Age correlation to angle lambda was insignificant. Average PCI-x and PCI-y in all eyes was - 0.047 mm and + 0.091 mm, respectively.

CONCLUSIONS

Angle λ is significantly larger in hyperopia than myopia, and the effect of age is insignificant. Pupil center offset was horizontally greater in hyperopia than in myopia. We therefore encourage the preoperative assessment of angle λ to avoid decentered ablation, especially when treating hyperopia.

Angle Kappa agreement between Scheimpflug tomography, combined placido Scheimpflug and combined slit scanning placido systems

PURPOSE

To compare the measured or calculated angle Kappa using Oculus pentacam HR, Sirius and Orbscan III devices.

PATIENTS AND METHODS

A prospective randomized cohort study, conducted on 47 eyes of 47 healthy orthotropic individuals, with an age range of 18-50 years and a corrected Snellen's distance visual acuity (CDVA) of 0.8 decimal or better. Angle Kappa is assessed directly using Orbscan® III software version 1.8.165.1. (Bausch and Lomb Rochester, New York, United States), while Pentacam® HR 1.21r.65 (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Sirius device (CSO, version 3.2.1.60, Costruzione Strumenti Oftalmici, Florence, Italy) were used to calculate angle kappa indirectly.

RESULTS

Least mean difference of estimated angle Kappa was between Orbscan and Pentacam devices (- 0.18° ± 1.8), and it was statistically insignificant (p value = 0.1294). Differences between both Orbscan and Sirius, and Pentacam and Sirius were statistically significant (p value = 0.0004 and < 0.0001 consecutively). Bland Altman analysis showed a 95% confidence interval between Orbscan III and Pentacam of - 3.76 to 3.4 and between Orbscan III and Sirius of - 3.79 to 2.26.

CONCLUSION

Pentacam parameters can be used as a reliable method to calculate angle kappa indirectly, without usage of any additional measurements from other machine. Sirius device parameters could also be used, but with less accurate results. A simple modification to those devices' software to calculate it, and incorporate it in the printout is possible, and highly recommended.

Dysphotopsias or Unwanted Visual Phenomena after Cataract Surgery

Dysphotopsias are unwanted visual phenomena that occur after cataract surgery. They represent some of the most common reasons for patient dissatisfaction after uncomplicated surgery for cataract phacoemulsification with in-the-bag intraocular lens (IOL) implantation. Depending on the form of the optical phenomenon and the effect it poses on vision, dysphotopsias are divided into positive and negative type. Positive dysphotopsias are usually described by patients as glare, light streaks, starbursts, light arcs, rings, haloes, or flashes of light. Negative dysphotopsias are manifested as an arc-shaped shadow or line usually located in the temporal part of the visual field, similar to a temporal scotoma. In addition to their different clinical manifestations, positive and negative dysphotopsia also have different risk factors. Even though up to 67% of patients may experience positive dysphotopsia immediately after surgery, only 2.2% of the cases have persistent symptoms up to a year postoperatively. Surgical intervention may be indicated in 0.07% of cases. The incidence of negative dysphotopsias is up to 26% of all patients; however, by one year postoperatively, the symptoms usually persist in 0.13 to 3% of patients. For both types of dysphotopsia, preoperative patients' education, accurate preoperative diagnostics, and use of an appropriate IOL design and material is mandatory. Despite all these measures, dysphotopsias may occur, and when noninvasive measures fail to improve symptoms, a surgical approach may be considered.

Finite element modeling of effects of tissue property variation on human optic nerve tethering during adduction

Tractional tethering by the optic nerve (ON) on the eye as it rotates towards the midline in adduction is a significant ocular mechanical load and has been suggested as a cause of ON damage induced by repetitive eye movements. We designed an ocular finite element model (FEM) simulating 6° incremental adduction beyond the initial configuration of 26° adduction that is the observed threshold for ON tethering. This FEM permitted sensitivity analysis of ON tethering using observed material property variations in measured hyperelasticity of the anterior, equatorial, posterior, and peripapillary sclera; and the ON and its sheath. The FEM predicted that adduction beyond the initiation of ON tethering concentrates stress and strain on the temporal side of the optic disc and peripapillary sclera, the ON sheath junction with the sclera, and retrolaminar ON neural tissue. However, some unfavorable combinations of tissue properties within the published ranges imposed higher stresses in these regions. With the least favorable combinations of tissue properties, adduction tethering was predicted to stress the ON junction and peripapillary sclera more than extreme conditions of intraocular and intracranial pressure. These simulations support the concept that ON tethering in adduction could induce mechanical stresses that might contribute to ON damage.

Angle κ and its effect on the corneal elevation maps in refractive surgery candidates

PURPOSE

To assess the associations of angle κ and Pentacam decentration indices with elevation maps in normal refractive surgery candidates.

SETTING

Salouti Cornea Research Center, Salouti Eye Clinic, Shiraz, Iran.

DESIGN

Retrospective observational study.

METHODS

In this research, the right eyes of 173 refractive surgery candidates were assessed. Data of front and back corneal elevation maps, keratometric data, decentration indices, and corneal astigmatism obtained by Pentacam HR system and angle κ obtained by Orbscan IIz were extracted. Maximum elevation (or depression) for each of the 4 quadrants was recorded. Correlations of elevation values with angle κ, Pentacam decentration indices, keratometry, and astigmatism were examined by Pearson correlation coefficient. 148 age- and sex-matched cases with keratoconus grade 1 were selected as a positive control group, and Pentacam variables were compared between the groups.

RESULTS

Overall, data from 173 eyes of 173 normal refractive surgery candidates and 148 eyes of 148 patients with keratoconus were recorded and analyzed. In normal refractive surgery candidates, the mean of angle κ was 5.32 ± 1.36 (SD) degrees. Angle κ had a positive correlation with front and back temporal elevations based on a best-fit sphere (BFS) ( r = 0.339, P = .001; r = 0.300, P < .001, respectively). Front and back keratometric astigmatisms were positively correlated with front and back nasal and temporal elevations ( r ≥ 0.543, P < .001) and negatively correlated with superior and inferior elevations ( r ≤ -0.547, P < .001). These associations no longer existed when using best-fit toric ellipse (BFTE) for calculating elevation data. The thinnest point to vertex decentration was significantly associated with the back temporal elevation (based on the BFTE) in both normal ( r = 0.311, P < .001) and keratoconus ( r = 0.190, P = .021) eyes.

CONCLUSIONS

This study showed that elevation maps obtained by the Pentacam system using BFS might be affected by both the large angle κ and corneal astigmatism, confounding the preoperative assessment of refractive surgery candidates. Using BFTE as a reference for calculating elevation data should eliminate most diagnostic issues and thus is encouraged in this context.

Extent of foveal fixation with eye rotation in emmetropes and myopes

PURPOSE

This pilot study aimed to investigate the maximum extension of foveal fixation in the horizontal direction among young adults in both emmetropes and myopes.

METHODS

35 participants (28 emmetropes and 7 myopes) were included. Participants with restricted extra-ocular mobility, end gaze nystagmus, and/or any other ocular pathology were excluded. Visual acuity (VA) was used as a surrogate measure of foveal fixation. VA was determined using a staircase procedure with 8 reversals. The average of the last 5 reversals was taken as the thresholds. VA acuity was measured at different gaze eccentricities along nasal and temporal visual field meridian. The eccentricity at which VA drops significantly was taken as the maximum extent of foveal fixation. A bilinear fit regression model was used to investigate the drop in the VA in both nasal and the temporal direction.

RESULTS

Emmetropes can foveate up to 35 ± 2° in nasal and 40 ± 3° in temporal direction and myopes can foveate up to 38° in both nasal and temporal directions. Paired student t-test showed a significant difference in foveal fixation between nasal and temporal direction for emmetropes (P<0.001) but not in myopes (P = 0.168). An unpaired student t-test showed a significant difference in foveal fixation for nasal direction between myopes and emmetropes (P = 0.01). However, no statistically significant difference was found in foveal fixation for temporal direction between myopes and emmetropes (P = 0.792).

CONCLUSION

The eye rotation does not necessarily match with the extent of foveal fixation at extreme eye rotation. Eyes can fixate only up to 35° nasally and 40° temporally maintaing their maximum visual acuity.

How vergence influences the perception of being looked at

Perceiving other people's direct gaze is important for many areas of everyday activity. For horizontal and vertical eye movements, the area of being looked at, known as the cone of gaze, has been well explored. Previous research has shown a range of eye rotations (up to eccentricities of 4°-9°) that people accept as direct gaze. Vergence is an important cue for perceiving the depth of fixation. This study examines the range of vergence angles that support the perception of being looked at. In two experiments, observers adjusted the degree of vergence of the lookers' eyes until they felt just (not) looked at. The first experiment also asked to adjust the point of being exactly looked at, which was 0° (parallel eyes). The thresholds of being just (not) looked at were around 4.5° of convergence and 2.5° divergence, which results in a depth of 7° of vergence. This depth was replicated in Experiment 2, while the thresholds of convergence (3.5°) and divergence (3.5°) slightly differ from Experiment 1. The results indicate a consistent area of vergences being accepted as direct gaze, yielding first-time evidence for a third dimension-the depth dimension-of direct gaze.

Angle Kappa Measurement and Its Correlation to Other Ocular Parameters in Normal Population by a New Imaging Modality

SIGNIFICANCE

This study obtained normative database for angle kappa using Orbscan 3. The average angle kappa was 2.3° ± 1.34 in the whole sample, 2.23° ± 1.36 in myopic eyes, and 3.3° ±1.5 in hyperopic eyes. This is very important for optimization of refractive surgery outcome.

PURPOSE

The aim of this cross-sectional study was to obtain the value of mean angle kappa in normal eyes of patients seeking laser vision correction, by the Orbscan 3.

METHODS

The study was conducted on healthy eyes of people seeking laser refractive surgery. 1815 eyes of 908 of candidates were included. These were examined as a part of preoperative assessment. Orbscan 3 was used to measure Angle kappa and its XY intercepts, keratometry readings, central corneal thickness (CCT), thinnest location (TL), white to white (WTW), and corneal asphericity of front surface (Qf) and back surface (Qb).

RESULTS

Mean angle kappa in all eyes was 2.3° ± 1.34. The value was 2.23° ± 1.36 in myopic eyes, 3.3° ±1.5 in hyperopic eyes, and 2.9° ±1.6 in emmetropic eyes. Positive correlation was found between angle kappa and age, spherical equivalent, subjective sphere, and WTW. On the other hand, axial length, average k, CCT, pupil diameter and asphericity Q front were negatively correlated to angle kappa.

CONCLUSIONS

Mean angle kappa value measured by the orbscan 3 was 2.3° ± 1.34. This could be attributed to different software used, in addition to the relatively high axial length in the studied eyes.

Characteristics of Pupil Offset in Young Asian Adults With Mild-Moderate and High Myopia

Purpose

The purpose of this study was to explore the characteristics of pupil offset in young Asian adults with myopia.

Methods

In total, 1200 eyes (600 young adults, 18–35 years old) were divided into mild-moderate and high groups according to equivalent spherical diopters (SEQ). The pupil offset and its X and Y components were compared between the groups. Linear correlation was analyzed among pupil offset, X and Y components, and SEQ. Multiple linear regression analysis was conducted for pupil offset and eye parameters.

Results

The mean age of all subjects was 22.5 ± 4.8 years. The mean magnitude of the pupil offset (0.18 ± 0.09 mm vs. 0.15 ± 0.08 mm) and Y component (0.12 ± 0.08 mm vs. 0.10 ± 0.07 mm) were larger in the high group than in the mild-moderate group (P < 0.05). The magnitude of pupil offset, X and Y components, and SEQ were positively correlated. The pupil center (PC) of the right eye in the mild-moderate group was mainly superotemporal to the corneal vertex and mainly superonasal for the left eye and both eyes in the high group. Multiple linear regression analysis revealed that the magnitude of pupil offset correlated with central corneal thickness, intraocular pressure, and mean corneal curvature (P < 0.05).

Conclusions

The magnitude of the pupil offset that correlated with partial eye parameters and its X and Y components increased as the SEQ increased, and the PC gradually shifted toward the superonasal direction in young Asian adults with myopia.

Translational Relevance

Subjects with high myopia with a larger pupil offset should be considered for better postoperative visual quality during refractive surgery.

Pupil barycenter configuration in patients with myopia and hyperopia

PURPOSE

To compare the apparent chord mu between hyperopia and myopia cases and investigate the usefulness of iris barycenter configurations as an alternative for performing kappa angle distance calculations.

METHODS

This prospective study evaluated 394 eyes of 197 patients classified into two groups according to their spherical equivalent values: the myopic (mean spherical equivalent refraction ≤  - 0.50 D) and the hyperopia group (mean spherical equivalent refraction ≥  + 0.50 D). The two groups were further subdivided according to severity (myopic group: mild, ≤  - 0.50 and ≤  - 3.00 D; moderate, <  - 3.00 and ≤  - 6.00 D; severe, <  - 6.00 D; hyperopic group: mild, ≥  + 0.50 and ≤  + 2.00 D; moderate, >  + 2.00 and ≤  + 4.00 D; severe, >  + 4.00 D). The pupil and iris barycenter distance measurements and other parameters were obtained through optical low-coherence reflectometry.

RESULTS

Of the 197 patients, 109 (55.3%) were female and 88 (44.7%) were male individuals; their ages ranged from 7 to 60 years (mean, 35.16 ± 14.75 years). The average pupil barycenter distances were 0.38 ± 0.15 and 0.21 ± 0.11 mm in hyperopia and myopia patients, respectively (p < 0.01). Corneal and lens thickness measurements were higher in hyperopia patients (p < 0.01, p < 0.01, respectively), whereas anterior chamber depth and pupil diameter measurements were higher in myopia patients (p < 0.01, p < 0.01, respectively). No significant difference in astigmatism or white-to-white measurements was observed between hyperopia and myopia patients (p > 0.05).

CONCLUSION

The measurements for the apparent chord mu of the pupil and iris barycenter origins were higher in hyperopic than in myopic cases.

Translation model for CW chord to angle Alpha derived from a Monte-Carlo simulation based on raytracing

Background

The Chang-Waring chord is provided by many ophthalmic instruments, but proper interpretation of this chord for use in centring refractive procedures at the cornea is not fully understood. The purpose of this study is to develop a strategy for translating the Chang-Waring chord (position of pupil centre relative to the Purkinje reflex PI) into angle Alpha using raytracing techniques.

Methods

The retrospective analysis was based on a large dataset of 8959 measurements of 8959 eyes from 1 clinical centre, using the Casia2 anterior segment tomographer. An optical model based on: corneal front and back surface radius Ra and Rp, asphericities Qa and Qp, corneal thickness CCT, anterior chamber depth ACD, and pupil centre position (X-Y position: Pup_X and Pup_Y), was defined for each measurement. Using raytracing rays with an incident angle I_X and I_Y the CW chord (CW_X and CW_Y) was calculated. Using these data, a multivariable linear model was built up in terms of a Monte-Carlo simulation for a simple translation of incident ray angle to CW chord.

Results

Raytracing allows for calculation of the CW chord CW_X/CW_Y from biometric measures and the incident ray angle I_X/I_Y. In our dataset mean values of CW_X = 0.32±0.30 mm and CW_Y = -0.10±0.26 mm were derived for a mean incident ray angle (angle Alpha) of I_X = -5.02±1.77° and I_Y = 0.01±1.47°. The raytracing results could be modelled with a linear multivariable model, and the effect sizes for the prediction model for CW_X are identified as Ra, Qa, Rp, CCT, ACD, Pup_X, Pup_Y, I_X, and for CW_Y they are Ra, Rp, Pup_Y, and I_Y.

Conclusion

Today the CW chord can be directly measured with any biometer, topographer or tomographer. If biometric measures of Ra, Qa, Rp, CCT, ACD, Pup_X, Pup_Y are available in addition to the CW chord components CW_X and CW_Y, a prediction of angle Alpha is possible using a simple matrix operation.

An Individual-Difference-Aware Model for Cross-Person Gaze Estimation

We propose a novel method on refining cross-person gaze prediction task with eye/face images only by explicitly modelling the person-specific differences. Specifically, we first assume that we can obtain some initial gaze prediction results with existing method, which we refer to as InitNet, and then introduce three modules, the Validity Module (VM), Self-Calibration (SC) and Person-specific Transform (PT) module. By predicting the reliability of current eye/face images, VM is able to identify invalid samples, e.g. eye blinking images, and reduce their effects in modelling process. SC and PT module then learn to compensate for the differences on valid samples only. The former models the translation offsets by bridging the gap between initial predictions and dataset-wise distribution. And the later learns more general person-specific transformation by incorporating the information from existing initial predictions of the same person. We validate our ideas on three publicly available datasets, EVE, XGaze, and MPIIGaze dataset. We demonstrate that our proposed method outperforms the SOTA methods significantly on all of them, e.g. respectively 21.7%, 36.0%, and 32.9% relative performance improvements. We are the winner of the GAZE 2021 EVE Challenge and our code can be found here https://github.com/bjj9/EVE_SCPT.

Comparison of preoperative angle kappa measurements in the eyes of cataract patients obtained from Pentacam Scheimpflug system, optical low-coherence reflectometry, and ray-tracing aberrometry

Background

Angle kappa plays a vital role in the implantation of multifocal intraocular lens (MIOL). Large angle kappa is related to a higher risk of postoperative photic phenomena. This study aims to compare preoperative angle kappa in the eyes of cataract patients obtained from the Pentacam Scheimpflug system (Pentacam), optical low-coherence reflectometry (Lenstar), and ray-tracing aberrometry (iTrace).

Methods

One hundred thirteen eyes of 113 patients with cataracts were included. Each eye was examined 3 times using all devices to obtain angle kappa and pupil diameter. When considering dependent eyes for one individual, angle kappa in both right eyes and left eyes should be analysed separately. The repeatability and reproducibility were evaluated using the within-subject standard deviation (Sw), repeatability (2.77 Sw), and intraclass correlation coefficient (ICC). The difference, correlation, and agreement between devices were evaluated by paired t-tests, Pearson tests, and Bland-Altman analysis, respectively.

Results

Intraoperator repeatability and interoperator and intersession reproducibility of angle kappa showed an Sw of less than 0.05 mm, a 2.77 Sw of 0.14 mm or less, and an ICC of more than 0.96. Angle kappa was not significantly different between Pentacam and Lenstar (P > 0.05), while angle kappa was significantly different between Pentacam and iTrace and between Lenstar and iTrace (P < 0.05). There was a strong correlation between Pentacam and Lenstar for angle kappa (r =0.907 to 0.918) and a weak or moderate correlation between Pentacam and iTrace and between Lenstar and iTrace (r =0.292 to 0.618). There were narrow 95% limits of agreement (LoA) between Pentacam and Lenstar for angle kappa and wide 95% LoA between Pentacam and iTrace and between Lenstar and iTrace. No significant differences in pupil diameter were found between Pentacam and Lenstar in either eye (P > 0.05). Positive angle kappa (nasal light reflex) was found in most cataract patients (79.25% to 84.91%) through 3 different devices in both eyes.

Conclusions

The 3 devices provided high intraoperator repeatability and interoperator and intersession reproducibility for angle kappa measurements. The measurement of preoperative angle kappa in the eyes of patients with cataracts by Pentacam and Lenstar has good agreement.

Prediction of CW chord as a measure for the eye's orientation axis after cataract surgery from preoperative IOLMaster 700 measurement data

BACKGROUND

The angles alpha and kappa are widely discussed for centring refractive procedures, but they cannot be determined with ophthalmic instruments. The purpose of this study is to investigate the Chang-Waring chord (position of the Purkinje reflex PI relative to the corneal centre) derived from an optical biometer before and after cataract surgery and to study the changes resulting from cataract surgery.

METHODS

The analysis was based on a large dataset of 1587 complete sets of preoperative and postoperative IOMaster 700 biometry measurements from two clinical centres, each containing: valid data for pupil and corneal centre position, the position of the Purkinje reflex PI originated from a coaxial fixation target, keratometry (K), axial length (AL), anterior chamber depth (ACD), lens thickness (LT), central corneal thickness CCT, and horizontal corneal diameter W2W. The Chang-Waring chord CW was derived from pupil centre and Purkinje reflex PI analysed preoperatively and postoperatively, and a multilinear regression model together with a feedforward neural network algorithm was set up to predict postoperative CW chord from preoperative CW chord, K and biometric distances of the eye.

RESULTS

The Y component of CW chord shows a slight shift in the inferior direction in both left and right eyes, before and after cataract surgery. The X component shows some shift in the temporal direction, which is more pronounced preoperatively and slightly reduced postoperatively but with a larger variation. The change in CW chord from preoperative to postoperative shows a slight shift in the superior and nasal directions. Our algorithms for prediction of postoperative CW chord using preoperative CW chord, keratometry and biometry as input data performed with a multilinear regression and a feedforward neural network approach were able to reduce the variance, but could not properly predict the postoperative CW chord X and Y components.

CONCLUSION

The CW chord as the position of the Purkinje reflex PI with respect to the pupil centre can be directly measured with any biometer, topographer or tomographer with a coaxial fixation light. The mean Y component does not differ between right and left eyes or preoperatively and postoperatively, but the mean temporal shift of the X component preoperatively is slightly reduced postoperatively, but with a larger scatter of the values.

The relationship between angle kappa and astigmatism after phacoemulsification with implanting of spherical and aspheric intraocular lens

Purpose:

To determine the significance of any association between either change in angle kappa (K°) or the rectilinear displacement (L, mm) of the first Purkinje image relative to the pupil center and unexpected changes in astigmatism after phacoemulsification.

Methods:

Orbscan II (Bausch and Lomb) measurements were taken at 1, 2, and 3 months after unremarkable phacoemulsification in patients implanted with spherical (group 1, SA60AT, Alcon) or aspheric (group 2, SN60WF, Alcon) nontoric IOLs. The outputs were used to calculate L. Astigmatism, measured by autorefractometry and subjective refraction, was subjected to vector analysis (polar and cartesian formats) to determine the actual change induced over the periods 1–2 and 2–3 months postop.

Results:

Chief findings were that the mean (n, ±SD, 95%CI) values for L over each period were as follows: Group 1, 0.407 (38, ±0.340, 0.299–0.521), 0.315 (23, ±0.184, 0.335–0.485); Group 2, 0.442 (45, ±0.423, 0.308–0.577), 0.372 (26, ±0.244, 0.335–0.485). Differences between groups were not significant. There was a significant linear relationship between (A) the change in K (ΔK = value at 1 month-value at 2 months) and K at 1 month (x), where ΔK =0.668-3.794X (r = 0.812, n = 38, P = <0.001) in group 1 and ΔK = 0.263x -1.462 (r = 0.494, n = 45, P = 0.002) in group 2, (B) L and the J₄₅ vector describing the actual change in astigmatism between 1 and 2 months in group 2, where J₄₅ (by autorefractometry) =0.287L-0.160 (r = 0.487, n = 38, P = 0.001) and J₄₅ (by subjective refraction) =0.281L-0.102 (r = 0.490, n = 38, P = 0.002), and (C) J₄₅ and ΔK between 2 and 3 months in group 2, where J₄₅ (by subjective refraction) =0.086ΔK-0.063 (r = 0.378, n = 26, P = 0.020).

Conclusion:

Changes in the location of the first Purkinje image relative to the pupil center after phacoemulsification contributes to changes in refractive astigmatism. However, the relationship between the induced change in astigmatism resulting from a change in L is not straightforward.

Distribution of preoperative angle alpha and angle kappa values in patients undergoing multifocal refractive lens surgery based on a positive contact lens test

Purpose

To assess the preoperative objective angle alpha and angle kappa measurements of patients deciding to undergo multifocal refractive lens surgery based on a subjective positive multifocal contact lens test (MCLT).

Methods

Retrospective, consecutive case series. Alpha and kappa angles were measured using the iTrace aberrometer. All patients also performed a 1-week MCLT. Only patients with a positive MCLT underwent surgery. Visual outcome (UCVA) was obtained in the 1-year follow-up. We assessed the preoperative distribution of angle values within MCLT positive and negative patient groups.

Results

Two hundred seventeen eyes (111 patients) were included. Mean age was 56.4 years (SD 5.6) and 46.9% were female. In 71 eyes (38 patients), MCLT was positive. Of them, 12 eyes (17%) had an angle alpha and angle kappa ≥ 0.5mm. Of 146 eyes (73 patients) who refrained from surgery due to a negative MCLT, 71 eyes (48.6%) had both angles small (<0.5mm). In the 1-year follow-up, UCVA improved by 0.68 logMAR (SD 0.51; p<0.001) from baseline. Eyes with both small angle alpha and kappa sizes improved by 0.78 logMAR (SD 0.56), as did eyes with high (≥0.5mm) angle sizes (0.82 logMAR (SD 0.53). UCVA of eyes (n=24) with high alpha but low kappa sizes improved less (−0.31 logMAR (SD 0.13; p=0.019)).

Conclusion

Four out of five patients with a positive MCLT also had correspondingly small angle values. One-half of patients with low preoperative angle values refrained from surgery due to a negative MCLT result. One-year visual acuity improvement was substantial and independent from angle sizes.

Distribution of Pupil Offset and Angle Kappa in a Refractive Surgery Preoperative Population of 750 Myopic, Emmetropic, and Hyperopic Eyes

PURPOSE

To report the distribution of pupil offset and angle kappa in 750 myopic, emmetropic, and hyperopic eyes presenting for refractive surgery.

METHODS

A retrospective study included 750 consecutive eyes screened for corneal refractive surgery between January 2006 and February 2013. The eyes were divided into three equal groups based on manifest refraction spherical equivalent (SEQ): emmetropic group between -0.25 and +0.50 diopters (D) and cylinder up to 1.00 D, myopic group greater than -0.50 D, and hyperopic group greater than +0.50 D. Angle kappa was measured with the Orbscan II software (Bausch & Lomb, Inc) and pupil offset defined as the distance at the corneal plane between the corneal vertex and the pupil center. Correlations with SEQ, cylinder, scotopic pupil diameter, average keratometry, and age were performed.

RESULTS

All results are reported for myopic, emmetropic, and hyperopic groups, respectively. Mean SEQ was -4.84 ± 2.89 D (range: -0.88 to -14.00 D), +0.21 ± 0.23 D (range: -0.25 to +0.50 D), and +2.44 ± 1.58 D (range: +0.63 to +7.75 D). Mean pupil offset magnitude was 0.27 ± 0.14 mm (range: 0.00 to 0.68 mm), 0.34 ± 0.14 mm (range: 0.02 to 0.78 mm), and 0.39 ± 0.13 mm (range: 0.07 to 0.75 mm). Mean pupil offset X-component was -0.18 ± 0.18, -0.28 ± 0.16, and -0.34 ± 0.15 mm (temporally displaced from the corneal vertex). Mean pupil offset Y-component was 0.06 ± 0.15, 0.03 ± 0.16, and 0.01 ± 0.16 mm (superiorly displaced from the corneal vertex). Multivariate linear regression for pupil offset magnitude found statistically significant variables were SEQ, cylinder, scotopic pupil diameter, and average keratometry. For pupil offset X-component, significant variables were SEQ, cylinder, and scotopic pupil diameter. For pupil offset Y-component, significant variables were SEQ and scotopic pupil diameter. Mean angle kappa was 5.28 ± 1.49°, 6.14 ± 1.44°, and 5.77 ± 1.29°.

CONCLUSIONS

Contrary to common belief, a pupil offset is present in the vast majority of eyes regardless of refractive error, with the mean temporal offset of at least 0.18 mm. Confirming previous studies, the largest pupil offset was found in the hyperopic group. However, there was also a wide range of pupil offset in myopic and emmetropic eyes. Correlations with SEQ and keratometry support the theory that pupil offset is also correlated with axial length. [J Refract Surg. 2021;37(1):49-58.].

Distribution of angle α and angle κ in a population with cataract in Shanghai

PURPOSE

To describe the distribution of angle α and angle κ in a population with cataract in Shanghai.

SETTING

Eye and Ear, Nose, Throat Hospital, Fudan University, Shanghai, China.

DESIGN

Hospital-based, cross-sectional study.

METHODS

Angle α, angle κ, and other ocular biometric parameters were determined by IOLMaster 700. The distributions of angle α and angle κ and their associations with systemic and ocular parameters were assessed.

RESULTS

This study included 15 127 eyes of 15 127 cataract patients. The mean angle α and angle κ values were 0.45 ± 0.21 mm and 0.30 ± 0.18 mm, respectively. Angle α and angle κ were both predominantly located temporal to the visual axis. A greater angle α or angle κ was associated with older age, lower corneal power, shorter white-to-white distance, and shallower anterior chamber depth (all P < .05). Angle α correlated positively with angle κ. With increasing axial length (AL), angle α gradually decreased in a nonlinear way and shifted to the nasal side of the visual axis, whereas angle κ decreased in eyes with AL less than 27.5 mm but increased again in eyes with longer AL.

CONCLUSIONS

Angle α and angle κ, both predominantly located temporal to the visual axis, were influenced by multiple anterior segment parameters. As AL increased, the changes in angle α and angle κ were nonlinear, and their locations gradually shifted from the temporal to the nasal side of the visual axis.

Distinct differences in anterior chamber configuration and peripheral aberrations in negative dysphotopsia

Clinical evaluations combined with ray-tracing analyses in patients with negative dysphotopsia supported the role of an increased angle κ.

Purpose:

To provide insights into the anatomical characteristics associated with negative dysphotopsia using quantitative clinical data.

Setting:

Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands.

Design:

Case-control study.

Methods:

Anterior chamber tomography and peripheral aberrometry were measured in 27 pseudophakic patients with negative dysphotopsia and 30 pseudophakic control subjects. Based on these measurements, the total corneal power, anterior chamber depth, pupil location and diameter, iris tilt, and peripheral ocular wavefront up to 30 degrees eccentricity were compared between both groups. In addition, ray-tracing simulations using pseudophakic eye models were performed to establish a connection between these clinical measurements and current hypotheses on the etiology of negative dysphotopsia.

Results:

Twenty-seven patients with negative dysphotopsia and 25 pseudophakic controls were included in the analysis. The patients with negative dysphotopsia had a smaller (P = .03/P = <.01) and more decentered (P < .01) pupil than that of the pseudophakic controls. In addition, an increased temporal-tilted iris (P < .01) and an asymmetric peripheral aberration profile were observed in patients with negative dysphotopsia, of which the latter was also apparent in several ray-tracing models. The combination of these in vivo results and ray-tracing simulations indicated that patients with negative dysphotopsia had a temporal-rotated eye, which confirmed the hypothesized relation between negative dysphotopsia and an increased angle κ.

Conclusions:

Patients with negative dysphotopsia had a smaller pupil and an increased angle κ, which made them more susceptible to experiencing a shadow in the temporal visual field.

Pseudo-Gaze Deviation Resulting From Positive Angle Kappa and Esotropia

ABSTRACT

A 6-year-old boy was referred for constant right gaze deviation. Rather than a gaze deviation, he constantly seemed to look on the left side of any displayed target. Examination revealed the association of a highly positive angle Kappa and an esotropia of equal values. He also exhibited signs of ocular albinism with no associated infantile nystagmus syndrome. The X-linked ocular albinism was confirmed genetically, explaining the presence of a positive angle Kappa. A highly positive angle Kappa can be associated with a convergent strabismus; in case both values offset each other, this can result in a constant "sidelooking," which should not be confused with a gaze deviation.

Evaluation of a Hirschberg Test-Based Application for Measuring Ocular Alignment and Detecting Strabismus

Purpose: Photographic Hirschberg test applications are practical options for screening in areas where a specialist is not available. A semi-automated Hirschberg test-based application was developed and evaluated on its ability to detect and measure strabismus at distance and near fixation.Methods: This is a prospective cross-sectional inter-rater agreement study conducted at a tertiary hospital. Study A evaluated the ability of the application to determine the presence or absence of strabismus in subjects of unknown strabismus status (n = 28). Study B evaluated the ability of the application to measure the deviation of strabismic subjects (n = 8). All subjects underwent alternate prism cover test (APCT) at distance and near fixation. Facial photographs at distance and near fixation were taken. Each photograph underwent automated face and eye detection, manual limbus and corneal reflex identification, and strabismus detection and measurement.Results: The application obtained a matching rate of 95.14% for the face and eyes. The application yielded a sensitivity of 92.86% for horizontal strabismus at distance and near fixation, however, with low specificity values (7.692%, 14.81%, and 8%). The Bland-Altman plots derived from Study B showed bias values of application measurements between 3.625Δ and 6.125Δ with wide intervals of the limits of agreement. Repeatability of the measurements yielded bias values of -0.625Δ and 2.5Δ for horizontal and vertical strabismus at distance and 4.375Δ and 1.25Δ at near fixation, respectively.Conclusion: This semi-automated Hirschberg test-based application can effectively determine the face and eye location and shows potential as a screening tool for horizontal strabismus.

Determination of Optic Axes by Corneal Topography among Italian, Brazilian, and Chinese Populations

This study aims to describe a new universal method to identify the relative three-dimensional directions of visual, pupillary, and optical axes of the eye and the angles between them using topography elevation data. The method was validated in a large clinical cohort, and ethnical differences were recorded. Topography elevation data were collected from 1992 normal eyes of 966 healthy participants in Italy, Brazil, and China. The three main axes were defined as follows: optical axis (OA) was defined as the optimal path of light that passes through the ocular system without refraction. The pupillary axis (PA) line was defined using X and Y coordinates of the pupil centre with the chamber depth, in addition to the centre of a sphere fitted to the central 3 mm diameter of the cornea. The visual axis (VA) was taken by its best approximation, the coaxially sighted corneal light reflex. The alpha angle was measured between the VA and OA, and the kappa angle between the VA and PA. The average values of kappa and alpha angles were 3.41 ± 2.84 and 6.04 ± 2.43 in the Italian population, 2.6 ± 1.53 and 5.87 ± 2.3 in the Brazilian population, and 2.09 ± 1.22 and 3.85 ± 1.48 in the Chinese population.

Influence of angle Kappa on the optimal intraocular orientation of asymmetric multifocal intraocular lenses

PURPOSE

to evaluate the effects of kappa angle and intraocular orientation on the theoretical performance of asymmetric multifocal intraocular lenses (MIOL).

METHODS

For a total of 21 corneal aberrations, a computational analysis simulated the implantation of a computationally designed MIOL. An image quality parameter (IQ) (visually modulated transfer function metric) was calculated for a 5.0-mm pupil and for three conditions: distance, intermediate, and near vision. The procedure was repeated for each eye after a rotation of the MIOL with respect to the cornea from 0º to 360º in 5º steps. Kappa angles from 0 to 900 microns, in 150 microns steps, combined with two two variants of MIOL centration were tested: in the corneal apex or in the center of the entrance pupil. A p-value ≤ 0.05 was considered significant.

RESULTS

There were statistically significant differences of the IQ depending of the intraocular orientation of the MIOL. If kappa angle was increased, there was a statistically significant decrease of the IQ. The IQ maintained stable when the optimal intraocular orientation was re-calculated for each kappa angle. In general, the inter-variability of the results between subjects was very high. There were no strong evidences supporting that there exists a preferable centration point.

CONCLUSIONS

Our results suggest that kappa angle theoretically affects significantly the performance of asymmetric MIOL implantation. However, its negative effect can be compensated if a customized intraocular orientation is calculated taking into account the presence of the kappa angle.

Analysis of excimer laser treatment outcomes and corresponding angle κ in hyperopic astigmatism

PURPOSE

To investigate the prevalence of preoperative, intraoperative, and postoperative angle κ in hyperopic eyes and its effect on the refractive outcomes of excimer laser vision correction.

SETTING

University Hospital Hamburg and Care Vision Refractive Centers, Germany.

DESIGN

Retrospective multicenter study.

METHODS

Hyperopic patients after laser in situ keratomileusis and before retreatment because of hyperopic regression were included. Three treatment groups were defined based on the magnitude of preoperative angle κ defined as low (<0.25 mm), moderate (0.25 to 0.50 mm), or high (>0.50 mm).

RESULTS

The study analyzed 170 hyperopic eyes of 112 patients (mean age 29.8 years ± 10.04 [SD], range 21 to 62 years). The preoperative angle κ was low, moderate, or high in 23, 49, and 98 cases, respectively. In eyes with a preoperative angle κ of 0.25 mm or more, changes in the x-axes and y-axes of angle κ and its magnitude were statistically significant (P < .05) between preoperative and intraoperative measurements. In these eyes, intraoperative angle κ (offset) was statistically significantly smaller (P < .05), and Purkinje images were statistically significantly more caudal (P < .001). Treatment predictability was independent from using preoperative or intraoperative angle κ, and there were no statistically significant differences in efficacy or safety.

CONCLUSIONS

A preoperative magnitude of angle κ as high as 0.50 mm or higher was present in more than 50% of regressed hyperopic eyes. Measuring angle κ preoperatively did not reflect its real-time intraoperative magnitude. Using the preoperatively larger angle κ as an intraoperative offset might result in a too nasally centered ablation that causes topographic and optical drawbacks; therefore, centering the ablation based on the intraoperative measured offset is recommended.

Scheimpflug vs Scanning-Slit Corneal Tomography: Comparison of Corneal and Anterior Chamber Tomography Indices for Repeatability and Agreement in Healthy Eyes

Purpose

To evaluate and compare the repeatability and agreement of Scheimpflug vs scanning-slit tomography of the cornea and the anterior chamber in terms of keratometric and tomographic indices in healthy eyes.

Methods

The 20 eyes of 10 healthy participants underwent 3 consecutive measurements using both Scheimpflug-tomography and scanning-slit tomography, diagnostic devices. Multiple corneal and anterior chamber tomographic parameters were recorded and evaluated to include corneal keratometry and its axis; corneal best-fit sphere (BFS), pachymetry mapping, angle kappa, anterior chamber depth (ACD), pupil diameter, and location. Repeatability for each device was assessed using the within each subject standard deviation of sequential exams, the coefficient variation (CV) and the intraclass correlation coefficient (ICC). Agreement between the two devices was assessed using Bland-Altman plots with 95% limits of agreement (LoA) and correlation coefficient (r).

Results

Both devices were found to have high repeatability (ICC>0.9) both in keratometric and other tomographic measurements. Scheimpflug tomography's repeatability though appeared superior in the average keratometry values, anterior and posterior BFS, thinnest corneal pachymetry value and location (p<0.05). Agreement: Statistically significant inter-device differences were noted in the mean values of K1, K2, BFS, ACD and thinnest corneal pachymetry (p<0.05). Despite the agreement differences noted, the two devices were well correlated (r>0.8) in respective measurements with Scheimpflug delivering consistently lower values than the scanning-slit tomography device.

Conclusion

Scheimpflug-tomography repeatability was found to be superior to that of scanning-slit tomography in this specific study, in most parameters evaluated. Inter-device agreement evaluation suggests that reading from the two devices may not be used interchangeably in absolute values, yet they are well correlated with Scheimpflug delivering consistently lower values in most.

Clinical outcomes of corneal refractive surgery comparing centration on the corneal vertex with the pupil center: a meta-analysis

PURPOSE

To compare the visual and refractive outcomes between centration on the corneal vertex and the pupil center in corneal refractive surgery.

METHODS

A comprehensive literature search was conducted using PubMed, MEDLINE, EMBASE, and the Cochrane Library to identify relevant studies. The primary outcomes were the postoperative spherical equivalent (SE), effectiveness [uncorrected distance visual acuity (UDVA) ≥ 20/20, eyes within ± 0.50 diopter (D) of target refraction], and safety [loss ≥ 2 lines of corrected distance visual acuity (CDVA)]. Higher-order aberrations were considered secondary outcomes.

RESULTS

Seven studies describing a total of 1964 eyes were included in this meta-analysis. A statistical significance in postoperative SE was found between the two centration methods for the correction of myopia that favor the CV-centered method (p < 0.001). No significant differences were observed in the proportion of eyes with UDVA ≥ 20/20 or loss ≥ 2 lines of CDVA postoperatively. However, the proportion of eyes within ± 0.50 D was slightly higher (p = 0.02) and the coma aberration was much lower in the corneal vertex-centered method (p < 0.001).

CONCLUSION

Preferable visual and refractive outcomes could be achieved with either centering on the corneal vertex or pupil center in corneal refractive surgery; however, the corneal vertex-centered method has shown partial benefits in some clinical indices. In order to obtain higher quality of clinical evidences, more randomized controlled trials (RCTs) are required in further investigations.

Vision Development Differences between Slow and Fast Motor Development in Typical Developing Toddlers: A Cross-Sectional Study

Many studies have established a relationship between visual function and motor development in toddlers. This is the first report to study two-year-olds via an assessment of their visual and motor skills. The purpose of this study is to describe the possible changes that can occur between visual and motor systems in typical developing toddlers. A total of 116 toddlers were included in this observational, descriptive, and cross-sectional study. Their mean age was 29.57 ± 3.45 months. Motor development variables studied were dominant hand/foot; stationary, locomotion, object manipulation, grasping, visual motor integration percentiles; gross motor, fine motor, and total motor percentiles; and gross motor, fine motor, and total motor quotients. Visual development variables were assessed including visual acuity, refractive error, ocular alignment, motor fusion and suppression, ocular motility, and stereopsis. Our findings demonstrated that typical developing toddlers with slow gross motor development had higher exophoria and further near point of convergence values compared to toddlers with fast gross motor development (p < 0.05). No statistically significant differences were found in visual acuity and stereopsis between slow and fast gross motor development toddlers.

The Effect of Intraoperative Angle Kappa Adjustment on Higher-Order Aberrations Before and After Small Incision Lenticule Extraction

PURPOSE

To compare higher-order aberrations (HOAs) after small incision lenticule extraction (SMILE) in patients with and without intraoperative angle kappa adjustments.

METHODS

This is a retrospective case series. One hundred six eyes of 106 patients who underwent SMILE at Tianjin Eye Hospital (Tianjin Medical University, Tianjin, China) for correction of myopia and myopic astigmatism were divided into 2 groups. The first group consisted of eyes with intraoperative angle kappa adjustment and the second group consisted of eyes without adjustment. Preoperative and postoperative visual outcome, refraction, and HOA measurements at 1 and 3 months were compared.

RESULTS

At the pupil size of 6 mm, vertical coma at 1 and 3 months after SMILE for the angle kappa-adjusted group was 0.153 ± 0.107 and 0.157 ± 0.094 μm, which were significantly lower than those of the nonadjusted group (0.204 ± 0.117 and 0.203 ± 0.113 μm, respectively) (P = 0.026 at 1 mo, P = 0.047 at 3 mo). The change in vertical coma between preoperative and postoperative measurements was 0.011 ± 0.136 and 0.023 ± 0.129 μm at 1 and 3 months postoperatively for the angle kappa-adjusted group, which were lower than those of the nonadjusted group (0.082 ± 0.165 and 0.085 ± 0.150 μm, respectively) (P = 0.023 at 1 mo, P = 0.045 at 3 mo). Subgroup analysis for eyes with large angle kappa demonstrated that the vertical coma was significantly less in the angle kappa-adjusted group at both 1 and 3 months (P = 0.009, P = 0.043, respectively). No significant correlation was observed between angle kappa and HOAs in the angle kappa-adjusted group.

CONCLUSIONS

Adjustment of angle kappa during SMILE resulted in less HOAs. It would provide more insight on how to optimize treatment centration in SMILE.

Influence of Angle κ and Higher-Order Aberrations on Visual Quality Employing Two Diffractive Trifocal IOLs

Prospective, randomized, comparative, and controlled study to estimate the association between angle κ distance and higher-order aberrations (HOAs) with postoperative visual acuity after presbyopia-correcting IOL implantation. Forty-three eyes from 43 patients were included and randomly assigned in two groups for either AT LISA tri 839MP or Acrysof IQ PanOptix IOL implantation. The OPD-Scan III analyzer was utilized to assess the angle κ distance and higher-order aberration (HOAs). Twenty-three eyes were in the Acrysof IQ PanOptix group and 20 patients in the AT LISA tri 839MP group. The uncorrected distance visual acuity (UDVA) for the PanOptix group was 0.092 ± 0.10, whereas for AT LISA tri was 0.050 ± 0.06 (P=0.229). The uncorrected intermediate visual acuity (UIVA) for the PanOptix group was 0.173 ± 0.18, whereas for AT LISA tri, it was 0.182 ± 0.11 (P=0.669). Uncorrected near visual acuity (UNVA) was 0.068 ± 0.04 and 0.085 ± 0.07, respectively (P=0.221). Also, correlation coefficient between HOAs and the Strehl ratio for each group were −0.768 (P < 0.0001) and −0.863 (P=0.0001). Patients implanted with both trifocal IOLs showed excellent postoperative visual performance at all distances at the six-month follow-up visit. No association was found between angle κ distance and postoperative visual acuity regardless of the angle κ magnitude or the two trifocal IOLs inner optical diameter. Also, internal aberrations demonstrated a significant inverse correlation with the Strehl ratio for both trifocal IOLs.

Review on Centration, Astigmatic Axis Alignment, Pupil Size and Optical Zone in SMILE

The advent of "flapless" small-incision lenticule extraction (SMILE), employing all-in-one technology, has resulted in a revolutionary breakthrough in refractive surgeries. SMILE has been gaining popularity due to fewer potential complications, such as postoperative dry eyes and greater biomechanical stability, etc. However, attention must be given to 1) the centration on the corneal vertex, 2) the proper alignment of the astigmatic axis, and 3) the relationship between pupil size and treatment diameter, to achieve good SMILE results. There is no pupil-tracking system to ascertain the accuracy of centration during the SMILE surgery. To improve the centration accuracy, our center uses two corneal topographers (Pentacam and Sirius) to measure and determine corneal vertex. Proper predicted optical zone diameter is not clearly defined yet in SMILE. Some scholars insist that mesopic pupil size should be taken into consideration when setting the predicted optical zone. Meanwhile, the issue of "functional optical zone" still has many unresolved issues and warrants further studies.